Armed with a rocket-propelled grenade launcher and an automatic rifle, a rogue Afghan soldier attacked a group of British troops early Tuesday in southern Afghanistan, killing three of the soldiers and wounding four others before escaping.
The Afghan soldier was assigned to a patrol base shared by NATO troops and the Afghan National Army in the volatile southern province of Helmand, according to NATO spokespeople and Afghanistan's Defense Ministry.
Helmand is where American troops mounted a large-scale offensive earlier this year to uproot Taliban insurgents from a stronghold in the town of Marjah.
The motive for the attack in the Nahr-e-Saraj district remained unclear, but it could prove deeply embarrassing for both the Afghan government and U.S. military leaders, who have stressed the importance of ratcheting up the training of Afghan security forces so that they can gradually take on more responsibility for securing their own country.
The Associated Press reported that Afghan President Hamid Karzai sent a letter of apology to the British government.
Karzai's spokesman, Waheed Omar, said Karzai "was upset to hear this. … It's a very regrettable case, and we hope that this is thoroughly investigated."
NATO and the Afghan Defense Ministry have begun a joint investigation. In a statement released by NATO, U.S. Army Gen. David Petraeus, commander of the U.S. and international forces in Afghanistan, said Afghan and NATO security forces "must ensure that the trust between our forces remains solid in order to defeat our common enemies."
Attacks by renegade Afghan soldiers or police on NATO troops are rare but have occurred in the past.
Tuesday's attack is likely to renew concerns about the infiltration of Taliban militants or sympathizers into Afghan security forces.
Last November, an Afghan police officer killed five British soldiers at a training base in Helmand province. A month later in the northwest province of Badghis, an Afghan soldier shot and killed an American soldier and injured two Italian troops.